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MX 4000 32-bit 128MB Volt Mod

post #1 of 20
Thread Starter 
I'm fairly sure a volt mod is possible on this card since HWBOT has a full modded one in first place for this category. I hope this means that the voltage can be regulated by a pot.

MX4000.jpg

I highlighted where I should be concentrating. The IC reads 3CD0Y4K ACT08

I can't find an exact datasheet for it but any random ACT08 datasheet looks like the chip and most of them look similar. Does that look the correct area? Also which leg should I be looking to attach the pot to? To find measure points for the vGPU and vMEM do you normally follow the traces out from the chip?

Any help would be greatly appreciated.
    
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post #2 of 20
You need to find continuity between the +3.3v AGP 'finger' and a leg of the IC which also has contact to ground. Are there any other IC's though?

*btw- that IC looks like its for display output.. not GPUv redface.gif

-couple Q's as well: What is stock GPUv?
What is stock vMEM?
post #3 of 20
Thread Starter 
which one is the 3.3V AGP finger (by finger you mean the gold contact on the card that goes into the AGP slot right?) Is it standard which one is the contact for the 3.3v? There aren't any other IC that really matter. The only other two, besides the mem, are both labelled LM358 which I've read in other forums are amplifiers of some sort and nothing to do with the voltage (seem right?).

That is my other problem I have no idea where to start with deciding on where to measure both vGPU and vMEM. Some pointers on how to decide this would be appreciated. Is it just trial and error?
    
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post #4 of 20
LM358 is low power dual operation amp... runs on +5v input. Looks like a single resistor from the {-} to ground controls voltage output. I suspect these are indeed the voltage IC's for mem and GPUv. Datasheet here wink.gif

*according to your pic, caps and mosfets on the left side of the PCB are for GPUv.. and caps and mosfet on the right are for vMEM.. measure at the caps to read voltage.
post #5 of 20
Thread Starter 
Okay, from that datasheet it looks like pin 4 is ground. I can follow the trace from pin 4 to a surface mounted resistor labelled 306. Does that make sense? Changing the resistance here should increase the voltage? Adding a pot at the leg or on the SMD?

The second LM358 is on the back but I can't seem to find a resistor it goes to I will have to break out the DDM.

The attached picture shows the voltage values at each of the caps. I'm assuming the 1.40v is the vGPU and the 3.33 near the back is for the vMEM?
    
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post #6 of 20
3.3v is for input stage to each phase

1.4v = GPUv
2.5v = vMEM

*Any resistor type mod-point will have both:

continuity to the leg/pin if the IC in question
continuity to ground

So long as you have both of those, make note of your stock resistance level, and change resistance with a pencil first. You can safely pencil while running..just make sure you have verified continuity first, and DO NOT attempt to measure resistance while running... ONLY voltage wink.gif
post #7 of 20
Thread Starter 
I've attached a closeup of the area around LM358. The resistor labelled R200 is actually R2004 (covered by heatsink). Pin 4 has 0 ohms to ground and so does the side closest pin 4 on R2004 (makes sense since you can see the trace going straight to it). They measure 0 ohms between them. The other side of R2004 measures 1.94/1.95 ohms @ 20K to pin 4, although it starts at about .80 and takes about 15secs to get to 1.95 where it stays steady. Does this make it a candidate for adding a pot? If I add a pot straight to Pin/Leg 4 and lower the resistance this will raise the voltage? Should I grow some balls and shade R2004 to test?
    
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post #8 of 20
*one side of the resistor should have continuity [beep mode] to ground.. as well as the other side, toning out to the IC [this you have done].

So long as the other side of that resistor has continuity to ground.. I would put some pencil on it wink.gif
post #9 of 20
Thread Starter 
There was continuity from the other side of the resistor to ground so I shaded R2004. I shaded down to 1.78 but there was no change in voltage measured at the caps. Shaded down to 1.67 and still no change at the caps. About 5 minutes into it running the screen blinked once and went alternating blue and black lines. I erased the shading and it seems to work fine. Am I back to square one?
    
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post #10 of 20
need to poke around a bit more and chart out resistance and points that have continuity to each other & ground..

would you mind posting or linking a pic of the backside?
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